Process of making regenerated cellulose balloon fabric comprising shrinking with strong alkali and steam blasting and product produced thereby



United States Patent thee 2,809,089 Patented Oct. 8, 1957 PROCESS OFMAKING REGENERATED CELLU- LOSE BALLOON FABRIC COMPRISING SHRINK- INGWITH STRONG ALKALI AND STEAM ggASTING AND PRODUCT PRODUCED THERE- JohnK. Phillips, Peninsula, Ohio, and Arnold M. Sookne, Silver Spring, Md.,assignors to The Goodyear Tire & Rubber Company, Akron, Ohio, acorporation of Ohio No Drawing. Application August 11, 1954, Serial No.449,258

3 Claims. (Cl. 8-125) This invention relates to a process for treatingfabric and is particularly directed to a process for treatingregenerated cellulose compositions and to the compositions so treated.When regenerated cellulose compositions are treated according to thepractice of this invention, greatly superior balloon cloth can beproduced by coating the treated regenerated cellulose in the form offabric with a rubbery composition.

It has long been a problem in the fabrication of lighterthan-air shipsand balloons to prepare a fabric for the envelope which couples greatstrength and flex life with the ability of the fabric to withstand work.In order to increase the breaking strength of the fabric, heavier yarnshave been used which in turn cause greater air permeability in thefinished fabric. This is turn requires considerably more coatingmaterial so that the net result is a heavier bag-making material whichresults in less loadcarrying capacity for a given bag volume. On theother hand, when the yarns which make up the fabric have been madesmaller in an effort to get a closer weave, which in turn makes for lessair permeability and less coating composition, the fabric breakingstrength has been reduced.

Many attempts have been made to overcome these problems and to make afabric which combines the optimum conditions of high breaking strength,long flex life, and great ability to absorb work coupled with a closeweave which is comprised of small diameter yarns and a small amount ofcoating.

These difficulties have been largely overcome by the practice of thisinvention wherein enhanced strength, flex life and air permeability areobtained without increasing the Weight by subjecting a regeneratedcellulose fabric to a caustic treatment in order to increase the flexlife by increasing the crimp of the yarns followed by a steamblastingtreatment which flattens the yarns by forcing a volatilized compositionthrough the transverse plane of the fabric while the fabric is retainedbetween spaced apart confining elements. When the treated fabric iscoated with a rubbery cement, a superior balloon cloth is obtained.

It is a general object of this invention to improve the physicalcharacteristics of regenerated cellulose yarns and fabrics. It is afurther object of this invention to provide a process whereby the flexlife and breaking strength of regenerated cellulose yarns and fabricsare improved with out substantially increasing the gauge of the yarnsand fabrics. It is a further object of this invention to provide aballoon fabric which has a low air permeability and thus can be coatedwith a minimum amount of coating composition.

This invention is concerned primarily with a process for treatingregenerated cellulose compositions in the form of filaments, yarns orfabrics. Several different regenerated cellulose compositions arecurrently being marketed. Perhaps the most widely used of thesematerials is viscose 6-. rayon, which, as is well known, is made bytreating cellulosic compositions with a caustic followed by atreatmentwith carbon disulfide which partially dissolves the cellulose and formsmetallic cellulose xanthate and then treating the product thereof with acaustic solution in order to get all of the cellulose into solution.This composition is then spun or extruded into regenerating bathscontaining sulfuric acid, sodium sulfate, zinc sulfate and otherchemicals which regenerate the cellulose in the form of filaments. Thefilaments are then stretched and washed preparatory to fabricconstruction.

Another type of regenerated cellulose is known as Fortisan. Thiscomposition is made by treating a cellulosic composition with aceticacid in order to obtain cellulose acetate. The cellulose acetate is thenspun or extruded into threads. The threads or filaments are thenstretched and saponified by a soap process which replaces the acetateradicals with hydroxyl radicals and thus regenerates the cellulosicmaterial.

Still another regenerated cellulose is being marketed as X-36. Thismaterial is a high tenacity fiber which is similar to Fortisan. It ismade by treating cotton linters or wood pulp with acetic anhydride inorder to acetylate the cellulose to cellulose acetate. The celluloseacetate is dissolved in acetone and then extruded into air in the formof filaments. The filaments are then stretched and saponified, theacetate radicals being replaced with hy dr-oxyl radicals, thus producinga regenerated cellulose.

There are various other regenerated cellulose compositions which aregenerally modifications of the above discussed materials. This inventioncontemplates the inclusion of any regenerated cellulose material.

The regenerated cellulose materials may be in the form of filaments,yarns (threads) or fabrics. Normally, the invention will be practicedwith fabrics because of the ease and convenience of processing. Althoughany size yarn can be used, the yarn will normally be at least denier andwill have at least one turn per inch twist.

Fabrics made from regenerated cellulose yarns are known to be verystrong, but also quite brittle. The strength of the fabric makes it adesirable material for many applications, e. g. for balloon fabric, butthe brittleness often makes the fabric undesirable because it does nothave suflicient resistance to .repeated flexing. If the yarns areincreased in diameter the porosity is increased, thus necessitating anexcess amount of coating material when the fabric is used for purposessuch as balloon cloth. This invention is concerned with the preparationof regenerated cellulose fabric which has enhanced resistance to flexcracking without increasing the gauge and which can be coated with aminimum amount of rubbery coating material because the porosity has beendecreased without tightening the weave. These desirable qualities areadded to regenerated cellulose fabrics by treating the fabric first witha caustic which greatly improves the resistance to flexing by increasingthe crimp followed by a steam-blasting treatment which causes areorientation of the yarn filaments which make up the fabric with aconsequent clos ing of the interstices between the yarns withoutsubstantially tightening the weave.

The first step in the process of treating the regenerated cellulosematerials of this invention is to immerse the material in a causticsolution. Any of the customary strongly alkaline materials such as thestrong bases or caustics which have a high degree of ionization can beused in this process. These caustics are preferably used in the form ofat least .1 N solutions. Strong bases such as sodium hydroxide,potassium hydroxide, lithium hydroxide, barium hydroxideand strontiumhydroxide can be used. Also, the quaternary ammonium hydroxides, such asbenzyl trimethyl ammonium hydroxide, are useful'bases. However, thealkali metal hydroxides represent a pre ferred class of bases,particularly sodium hydroxide and potassium hydroxide. The length oftreatment and the temperature of the treating baths are not critical butit is obvious that there will be a balance between the time andtemperature of the treatment and the concentration of the caustic, anincrease in one permitting a decrease in another. It has been foundpreferable to treat the materials for a period of about 2 minutes to 10minutes and at a temperature of about 60 F. to 80 F.

When the regenerated cellulose is in the form of yarns or fabrics itmust be treated in a relaxed state in order to obtain the maximumeffect. Treatment of the regenerated cellulose with caustic in theabsence of tension is critical. Treatment without tension allows thematerial to relax and shrink. This makes possible a substantial increasein crimp and elongation, important factors in improving flex life. Table1 shows the significant increase in the very important crimp values.Crimp value is the difference in distance between two points on a yarnas it lies in a fabric and the same two points when the yarn has beenremoved and straightened, expressed as a percentage.

TABLE 1 Efie ct of tension on treated Fortisan fabric. Samples treatedwith 8.5% sodium hydroxide at 25 C. for 5 minutes The importance oftreating the regenerated cellulose while in a relaxed condition can beillustrated by further tests which are reported in Table 2. Samples ofFortisan fabric were treated at 78 F. for 5 minutes in a bath of sodiumhydroxide in water. One such fabric was treated in a relaxed conditionand another under slight tension. These fabrics, after drying, werecoated with a rubber coating composition; Thereafter, circular disks 4"in diameter were cut from each of the three coated fabrics. These diskswere subjected to test in such manner that one half of each disk wasalternately rotated 270 in opposite directions for 10 cycles, Each ofthese samples was shifted 45 until each quarter of each test sample hadbeen subjected to rotation about the mid-point of the disk. Thereafter,each sample was subjected to a burst test which is described as testD76-49 on pages 45 and 46 of the A. S. T. M. standards for textiletesting. The corresponding test disks which were not subjected to therotation were subjected to the same burst test. Table 2 gives the datacovering these comparative tests in percentage values which representthe relationship of the burst strength of the rotated samples with thatof the nonrotated samples.

This table thus shows the enhanced ability of the fabric to withstandwork when it is treated with caustic in a relaxed condition. The controlsamples showed a relationship of 71.3% between the burst strength of theflexed sample and the burst strength of the nonflexed sample, the latterbeing taken as When the same Fortisan was treated with caustic accordingto this invention, either 10% or 8.5% solution being employed, the burststrength of the fiexed samples, as compared with the nonflexed controls,increased markedly, thus showing the enhanced ability of the coatedfabric to withstand repeated flexing such as encountered in actualservice. It should be noted, however, that this improvement was obtainedwhen the caustic treatment was applied to the fabric in the relaxedstate. The third set of figures, which show the relationship betwcen theburst strength of a flexed sample of Fortisan treated with caustic whileunder slight tension and the burst strength of a nonflexed sample of thesame material, are lower even than the control. When the fabric wassubjected even to slight tension burst strength fell off greatly, thusdemonstrating that the caustic treatment must be conducted while thefabric is in a relaxed condition in order to achieve the desired result.

It has been found that the concentration of caustic in water may rangefrom about 2% by weight of caustic to about 12% by weight of caustic. Itis preferable that the concentration be maintained between about 3.5% byweight and 10% by weight. The importance of these conditions isillustrated in Tables 3 and 4.

TABLE 3 Efiect of time of immersion in various concentrations of alkalion properties of Fortisan fabric Time in Alkali 2 Minutes 5 Minutes 10Minutes Concentration of Alkali,

Percent Breaking Ultimate Breaking Ultimate Breaking Ultimate Strength,Elonga- Strength, Elonga- Strength, Elonga- Pounds tion, Pounds tion,Pounds tion,

Percent Percent Percent 166 17 163 19 160 20 22 None 178 7. 5 0 (WaterControl) 179 7. 6

1 0i 1" strip.

Time in Alkali Concentration of Alkali,

Percent 2 Minutes- 5 Minutes- Minutes Wor Work Work Factor 1 Factor 1Factor l The work factor is the product of the strength and the ultimateelongation of the yarns.

These tables illustrate that the alkaline treatment increases theability of regenerated cellulose compositions to absorb work with acorresponding decrease in brittleness and consequent great improvementin flex resistance.

After the regenerated cellulose materials have been treated with thealkali, the excess alkali, if any, may be removed by any of thecustomary methods such as washing with water or by neutralizing with aweak water solution of an acid.

The chemical treatment can be handled on a batch basis or on acontinuous basis. It is preferable to process the regenerated cellulosein the form of fabric on a continuous basis, maintaining the fabric in arelaxed state. This treatment greatly improves the elongation and theflex resistance but increases the air permeability of the fabric. Thisis illustrated by Table 5, which shows the results obtained on Fortisanfabric treated with alkali in the mill.

TABLE 5 of Fortisan fabric, mill-treated Alkali Warp Air Per- Sample N0. Cone, Finished Ultimate meabllity,

g./100 ml. Width, in. Elongation, ftfi/rnin/ft.

Percent Control None 41 9. 8 24. 7 1 9.7 37 16. 1 362 2 8. 4 37 16. 1185 Coupled with the chemical treatment discussed above which makespossible the production of a fabric having greatly enhanced physicalcharacteristics such as greater flex resistance, it has been found thata further treatment of the regenerated cellulose provides a fabric whichapproaches optimum conditions of strength, flex life and resistance toair permeability. V

The regenerated cellulose yarns or fabrics which have been treated whilein a relaxed state with a strong caustic are subjected to a furthertreatment in order to substantially reduce the porosity of the treatedfabrics which have been treated with the caustic while in fabric form orwhich have been woven from caustic treated yarns. This process, which ishereinafter generally referred to as steam blasting, contemplatesthe'substantially instantaneous application of heat at relatively hightemperatures to a wet fabric while it is being confined or restrained inits cross-sectional dimension.

In the steam-blasting of fabric, accordingto the present invention, theliquid contained in the fabric is instantaneously converted into vaporby the heat applied to the fabric. Since the fabric is restrained onboth surfaces, the expansive force of the vapor thus generated insidethe fabric is concentrated in the'longitudinal and transversedimensionsof the fabric. This force, which is in the nature of an explosionineach'of the yarns,

escapee 6,.- causesithe fibers or filaments thereof to spread and closethe weave. .This spreading of the fibers or the filaments of the yarnand closing the interstices in the weave re- .duces the gauge andporosity of the finished fabric.

In the steam blasting of fabric, it is desirable that thespaced-apartopposed confining surfaces applied to both sides of thefabric be heated and rigid so as to insure that the quick volatilizationof the liquid in the individual yarns of the fabric will produceinternal forces in the yarns such that they will spread and becomeflattened.

I It will be readily understood that the steam-blasting process of thepresent invention may be applied equally advantageously to a variety ofdifferent types of fabric construction or weave such, for example, astwill, sateen, plain Weave, basket weave or others, as well as to acombination of different constructions. In practicing the invention, itis customary to use yarns of at least denier for the fabricconstruction.

The steam-blasting process is applicable broadly to fabrics formed ofmultiple filament or fibrous yarns as opposed to the monofils and to theuse of any type of liquid which will satisfactorily wet the yarn.Wetting of the yarn contemplates the complete permeation of the yarns bythe liquid. Obviously, the selection of the liquid for application tothe fabric to be treated should be such that the yarns composing thefabric will not be dissolved or otherwise deleteriously affectedthereby.

Water alone has been found to be a satisfactory liquid since it iseconomical to use and creates no particular problem in connection withthe venting of the gas or vapor'formed as a by-product of the process.In the event that satisfactory penetration of the Water into the yarn isnot achieved with water alone, water solutions ofvarious wetting agents,detergents, and the like can be employed to advantage. For example,Water solutions of material can be used such as derivatives of thevarious fatty acids. Also, diisobutyl sodium sulfosuccinate, diamylsodium sulfosuccinate and dioctyl sodium sulfosuccinate (Aerosol OT) canbe used as a wetting agent. Various other volatilizable materials can beused as fabric saturants, either alone or in the form of a watersolution.

The steam-blasting process of the present invention may be carried outby several different forms of apparatus. The preferred machine is amodified conventional calendering apparatus wherein the heating elementsthereof will merely constrain the fabric to a predetermined gauge whileit is being treated. For best results, it is necessary that at least oneof the rolls have a metallic surface in contact with the saturatedfabric as it passes between the rolls. Although more difficult to handlein production operations, metal-surfaced rolls to confine and constrainthe fabric on both sides give the best results because more rapidvolatilization of the saturant and greater uniformity of the gauge isthus made possible.

The rolls of the apparatus may be heated by any suitable medium such,for example, as high pressure steam circulated through tubes intherolls, gas heated rolls or electrically heated rolls. employed tomaintain the temperature of'the rolls within certain predeterminedlimits and to prevent any marked fluctuation in the roll temperatures.

It is essential that at least one of the rolls be adjust ably mounted inorder to insure a predetermined degree of constraint upon the saturatedfabric as it passes therebetween.

The direct result of the steam-blasting of fabrics is that a much moredense fabric is produced having a lower gauge. This treated fabric, whencoated or subsequently processed, exhibits a much more satisfactoryfinished product in that a smaller quantity of coating compound will berequired to produce the desired result.

As previously indicated herein, the steam blasting process etfectschanges inside-the fabric-itself. The liquid Thermostatic controls maybe with which the fabric is saturated penetrates into the voids betweenthe several fibers or filaments comprising the yarns which are woveninto the fabric. When the heat is applied, instantaneously the liquid isvolatilized and the suddenly formed vapor, since it is prevented fromescaping except along the lateral or longitudinal dimension of thefabric itself, exerts a force which tends to rearrange the fibers orfilaments of the yarns causing them to spread out.

This redisposition of the fibers or filaments in the yarns comprisingthe fabric is brought about by what corresponds to an explosive actionof the liquid as it is changed into vapor form. Since, due to therestrictive action of the rigid surfaces above and below the fabric, theexplosive action is confined to the plane of the fabric, the filamentscan only move in that direction, hence the flattening effect.

The degree of porosity and gauge reduction is dependent upon the ratioof yarn diameter in the fabric to adjacent void spaces which may beclosed by the steam-blasting of the yarn. Fabric porosity has beenreduced by this process as much as 80%, and, in certain instances, hasapproached zero porosity. In some cases, the gauge of steam-blastedfabric has been reduced as much as 60%.

It should be explained also that the expression plane of the fabric asemployed is intended to mean that area defined by the lateral (width)and longitudinal (length) dimensions of the fabric.

A steam-blasting process such as that disclosed herein is described incopending application Serial No. 308,223, filed September 6, 1952, nowU. S. Patent 2,712,170, and is characterized by the instantaneousvolatilization of a liquid saturant by means of heated calender rollswhich are spaced at the ultimate gauge desired in the finished material.Because of the restraint on the top and the bottom, this treatmentcauses the filaments comprising the yarns to rearrange and this in turncauses a flattening of the yarns and consequent closing of theinterstices which cuts down the air permeability of the fabric. Also,because of the volatilization of the saturant, the'fabric comes from thesteam-blasting apparatus in a substantially dry state. This results in aballoon fabric which is strong and flexible and can be coated with athin coating of rubber or rubber-like material in order to provide aballoon cloth which approaches the optimum in the relationship of weightof the air bag to carrying capacity.

When the regenerated cellulose is in the nature of a fabric, the weaveof the fabric is not critical. However, certain considerations regardingthe fabric will enhance the optimum characteristics desired in thefinished product.

Tests have been made to determine the reduction in porosity. These testswere conducted according to the A. S. T. M. standard test D-737-46 fordetermining porosity (air permeability). Table 6 illustrates theimportance of steam-blasting in closing the interstices of the fabric.Sample 1, the control, was a 2 x 2 basket weave Fortisan fabric. Sample2 was the same fabric after being treated with 8.5% caustic. Sample 3was the same fabric tested after the caustic treatment and aftersteam-blasting. Samples 4, 5 and 6 illustrate the treatment of X-36square woven fabric under the conditions outlined above.

The following illustrative examples of the practice of this inventionare not intended as limitations thereon.

EXAMPLE 7 I A sample of 2 x 2 Fortisan basket weave fabric was treatedin skein form byimmersing it for 7 minutes at 25? C. in a solution ofsodium hydroxide of 12.7 Baum (97 grams per liter) concentration. Thefabric was then neutralized with acetic acid, rinsed and dried at 250F., all of these operations being performed with substantially notension. The finish-ed fabric showed a 65% increase in ultimateelongation, and after coating, the fabric demonstrated greatly enhancedflex resistance as compared with a corresponding fabric which has notbeen treated with alkali.

EXAMPLE 2 A sample of 2 x 2 Fortisan basket weave fabric was treated inopen-width form by immersing it for 5 minutes at 25 C. in a solution ofsodium hydroxide of 1l.9 Baum (90 grams per liter) concentration. Thefabric was neutralized and rinsed as described above. It was thensubjected to steam-blasting at a temperature of 250 F. Coated-fabricsmade from this material showed enhanced flex resistance, withoutincreased thickness.

EXAMPLE 3 The efiicacy of this invention has further been illustrated bysemiproduction procedures. Twenty-five yards of regenerated cellulosefabric were treated for a period of 7 minutes in a caustic bathcontaining a water solution of sodium hydroxide wherein the sodiumhydroxide was present in an amount of 97 gms. per liter. Thereafter, thefabric was removed from the caustic bath, the excess caustic wasneutralized with acetic acid and the fabric was dried. All of the stepsof this chemical treatment were performed without tension on the fabric.After the treated fabric was dried it was saturated with water. Thesaturated fabric, having a gauge of .009 inch, was then passed betweenthe rolls of a steam-blasting apparatus, the rolls being set so that thefinal gauge of the fabric was about .0055 inch. After the interstices ofthe fabric had been substantially closed by the steam-blasting process,the fabric was coated with a rubber base coating composition. Physicaltests have indicated that this coated fabric has greatly increasedresistance to flex cracking and thus greatly increased ability to resistrupturing over comparable fabrics which were not treated according tothe practice of this invention.

In the practice of this invention, any of the customary rubber,rubber-like or plastic coating compositions, conventionally compounded,can be used to coat the treated fabric. For example, natural rubber, therubbery copolymers of butadiene and styrene, such as GR-S,polychloroprene, the polymerization products of a major proportion of amonoolefin such as isobutylcne, and a minor proportion of a polyolefin,such as butadiene or isoprene, as exemplified by butyl rubber,polybutadiene, the rubbery copolymers of butadiene and acrylonitrile,polystyrene and other similar materials when suitably compounded, can beused as coating compositions in the practice of this invention where acoated fabric is desired.

Although this invention has been described in terms of balloon fabricswhich are coated fabrics, both coated and uncoated treated regeneratedcellulose fabrics are within the scope of the invention.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

We claim:

1. The process of making an improved fabric characterized by improvedflex life and having improved air permeability comprising the steps of(1) immersing a fabric made from regenerated cellulose for a period ofabout 2 to 10 minutes at a temperature of about 60 F. to F. in a causticbath containing about 2% to about 12% by weight of a strong baseselected from the group consisting of sodium hydroxide and potassiumhydroxide while the fabric is under substantially no tension andthereafter removing the excess base, (2) saturating the regeneratedcellulose yarns which comprise the fabric with an inert volatilizableliquid which has a boiling point lower than the degradation temperatureof the filaments which comprise the yarns, and (3) passing the saturatedfabric between heated spaced-apart cylinder rolls, at least one of saidheated cylinder rolls being constructed with a conductive metal surface,said rolls being adjusted to a predetermined opening which issubstantially less than the original gauge of the fabric to be passedtherebetween and adapted to readily heat the saturated fabric to atemperature sutficient to instantaneously volatilize the liquid fabricsaturant so that the instantaneous conversion of the liquid to a vaporexerts a force which is concentrated in the longitudinal and transversedimensions of the fabric to cause the yarns which comprise the fabric tobe rearranged and flattened to bring about a reduction in the gauge ofthe fabric of from 60 to 80% of the original gauge and a substantialclosing of the intersices of the fabric.

2. The process of making an improved fabric characterized by improvedflex life and having improved air permeability comprising the steps of(l) immersing a fabric made from regenerated cellulose in a caustic bathcontaining about 2 to 12% by weight of a strong base selected from thegroup consisting of sodium hydroxide and potassium hydroxide for aperiod of about 2 to 10 minutes at a temperature of about F. to F., saidimmersion being characterized by the absence of tension on the fabricand thereafter removing the excess base, (2) saturating the regeneratedcellulose yarns which comprise the fabric with an inert liquid whichvolatilizes at a temperature lower than that at which a deleteriouseffect is produced upon the yarns, (3) subjecting the saturated fabricto heat in excess of the boiling point of the liquid saturant in orderto instantaneously volatilize the liquid saturant While constrainingsaid fabric between heated spaced-apart confining surfaces in adirection normal to the plane of the fabric simultaneously with theheating so that the volatilization of the saturant exerts a force in theplane of the fabric which spreads the filaments comprising the yarns tocause the yarns to substantially close the interstices between theyarns.

3. The product of the process of claim 2.

References Cited in the file of this patent UNITED STATES PATENTS2,042,437 Taylor May 26, 1936 2,153,964 Lejeune Apr. 11, 1939 2,712,170Phillips July 5, 1955 FOREIGN PATENTS 15,352 Great Britain Nov. 21, 19071907 612,268 Great Britain Nov. 10, 1948

1. THE PROCESS OF MAKING AN IMPROVED FABRIC CHARACTERIZED BY IMPROVED FLEX LIFE AND HAVING IMPROVED AIR PERMEABILITY COMPRISING THE STEPS OF (1) IMMERSING A FABRIC MADE FROM REGENERATED CELLULOSE FOR A PERIOD OF ABOUT 2 TO 10 MINUTES AT A TEMPERATURE OF ABOUT 60*F. TO 80*F. IN A CAUSTIC BATH CONTAINING ABOUT 2% TO ABOUT 12% BY WEIGHT OF A STRONG BASE SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE AND POTASSIUM HYDROXIDE WHILE THE FABRIC IS UNDER SUBSTANTIALLY NO TENSION AND THERAFTER REMOVING THE EXCESS BASE, (2) SATURATING THE REGENERATED CELLULOSE YARNS WHICH COMPRISE THE FABRIC WITH AN INERT VOLATILIZABLE LIQUID WHICH HAS A BOILING POINT LOWER THAN THE DEGRADATION TEMPERATURE OF THE FILAMENTS WHICH COMPRISE THE YARNS, AND (3) PASSING THE SATURATED FABRIC BETWEEN HEATED SPACED-APART CYLINDER ROLLS, AT LEAST ONE OF SAID HEATED CYLINDER ROLLS BEING CONSTRUCTED WITH A CONDUCTIVE METAL SURFACE, SAID ROLLS BEING ADJUSTED TO A PREDETERMINED OPENING WHICH IS SUBSTANTIALLY LESS THAN THE ORIGINAL GAUGE OF THE FABRIC TO BE PASSED THEREBETWEEN AND ADAPTED TO READILY HEAT THE SATURATED FABRIC TO A TEMPERATURE SUFFICIENT TO INSTANTANEOUSLY VOLATILIZE THE LIQUID FABRIC SATURANT SO THAT THE INSTANTANEOUS CONVERSION OF THE LIQUID TO A VAPOR EXERTS A FORCE WHICH IS CONCENTRATED IN THE LONGITUDINAL AND TRANSVERSE DIMENSIONS OF THE FABRIC TO CAUSE THE YARNS WHICH COMPRISES THE FABRIC TO BE REARRANGED AND FLATTERED TO BRING ABOUT A REDUCTION IN THE GAUGE OF THE FABRIC OF FROM 60 TO 80% OF THE ORIGINAL GAUGE AND A SUBSTANTIAL CLOSING OF THE INTERSTICES OF THE FABRIC. 